Apparatus for the electrolytic treatment of wires

ABSTRACT

The invention concerns apparatus for obtaining an electrolyzing current density which is approximately uniform along a wire subjected to the electrolytic treatment and forming one electrode of the apparatus.

United States Patent Girard [54] APPARATUS FOR THE ELECTROLYTIC [21] Appl. No.: 730,314

52 us. c1. ..204/1 R, 204/2s,204/141,

204/010. 7, 204/211, 204/228 51 1m.c1. ..]B01k3/02,C23b 5/68 58 Field of Search ..204/21 1, 228, 272, 206, 207,

204/43, 141, l R, DIG. 7, 28

3,347,770 10/1967 Valles et al. ..204/228 3,441,494 4/1969 Oshima et al. ..204/228 3,474,009 10/1969 Wang ....204/206 X 3,272,727 9/1966 Schmeckenbecher ..204/43 X FOREIGN PATENTS OR APPLICATIONS 599,188 3/1948 Great Britain ..204/206 Primary Examiner-John H. Mack Assistant Examiner-I). R. Valentine Attorney-Fred Jacob, Ronald T. Reiling and Lewis P. Elbinger [57] ABSTRACT The invention concerns apparatus for obtaining an electrolyzing current density which is approximately uniform along a wire subjected to the electrolytic treatment and forming one electrode of the apparatus.

[56] References Cited UNITED STATES PATENTS 8 Claims, 7 Drawing Figures 2,737,488 3/1956 Gray ..204/206 l 2 41 4 r so 4 [f A ///A APPARATUS FOR THE ELECTROLYTIC TREATMENT OF WIRES The present invention relates to apparatus for the electrolytic treatment of wire, the invention being concerned with apparatus for obtaining, in the electrolytic treatment of a wire of which only one end is connected to the electrolyzing current source, an electrolyzing current density which is approximately uniform along this wire.

In known apparatus of this kind for effecting a cathodic deposition as uniformly as possible on a wire having constant linear resistance, or an anodic dissolution of such a wire, in the case where the wire can only be connected to the electrolyzing current source at one of its ends, that portion of this wire which is subjected to the electrolytic treatment is stretched in a tank containing the electrolyte, the said portion of the wire being immersed in the electrolyte and performing the function of the cathode or the anode, depending upon the circumstances, in the electrolyte under consideration, one of the ends of the said portion of thewire is connected to one of the poles of the electrolyzing current source, and an antagonistic electrode, hereinafter referred to as the counterelectrode and performing the function of the anode or the cathode according to the circumstances, is immersed in the-electrolyte and is connected to the other pole of the electrolyzing current source, this antagonistic electrode being in the form of a cylinder having the same axis as the said treated wire portion, or any other form which gives a uniform current distribution in the electrolyte in the neighborhood of the wire in any cross section of the apparatus perpendicular to the wire.

In apparatus of the kind under consideration, there is set up between the ends of the treated wire portion a potential difference which is due to the electrolyzing current passing through the wire. An additional potential difference may appear between the said ends when the wire portion under consideration is traversed by an additional current emanating from another electrolytic operation taking place simultaneously on another portion of the wire. The potential therefore varies along the wire. On the other hand the potential is usually constant along the counterelectrode and if it varies its variation along the counterelectrode does not follow the same law as the variation of the potential along the wire. Finally, the potential difference between the anode and the cathode in a section of the apparatus varies in accordance with the position of this section along the wire and consequently the current density around the wire in a section of the apparatus varies correspondingly as a function of this position. If the amplitude of the current density variation observed exceeds a certain critical value, the properties of the deposit or the dissolution effected are not satisfactory. It is therefore necessary, in order to obtain an appropriate electrolytic treatment, to ensure that the amplitude of the corresponding variation of the potential difference between the anode and the cathode remains below a corresponding critical value.

An object of the invention is to provide apparatus of the kind under consideration in which the amplitude of the variation of the potential difference between'the anode and the cathode is maintained below a critical value, as required, for example in the continuous manufacture of wires coated with thin magnetic films.

An apparatus according to the invention is characterized in that it comprises means for passing through the counterelectrode a compensating current of such value that the potential difference which appears during the electrolytic treatment between two points of the counterelectrode which are situated respectively in two particular sections of the apparatus is equal to that which is then set up between those points of the treated portion of wire which are situated respectively in these particular sections, in order to produce in these two sections the same 'potential difference between the anode and the cathode and consequently the same current density around the treated wire.

In any section of such an apparatus, the potential difference between the anode and the cathode generally assumes a valve which is different from the particular value which is obtained in the said particular sections, because the potential of the anode and that of the cathode vary in accordance with different laws as a function of the position of a section along the said treated portion of wire.

If the electrolyzing source is connected to one of the ends of the counterelectrode, the value of the potential difference between the anode and the cathode in any section situated between the said particular sections is constantly below the said particular value.

If the said electrolyzing current source is connected to a point of the counterelectrode which is situated between the said particular sections, it is possible by an appropriate choice of the resistance of the counterelectrode to obtain the said particular features, conditions, value of the potential difference under connsideration in two sections situated between the said particular sections and situated on either side of the section which contains that point of the counterelectrode which is connected to the electrolyzing current source. In an apparatus according to the invention which has such feqtures, the amplitude of the variations of the potential difference under consideration is reduced, under otherwise equal conditions as compared with that occurring in the other apparatus according to the invention.

In the apparatus according to the invention, if the variation of the potential along thetreated portion of wire is approximately linear, it is possible to obtain a low amplitude of variation of the potential difference between the anode and the cathode by also making approximately linear the variation of the potential along the counterelectrode by an appropriate choice of the resistance of the wire of which this counterelectrode is formed.

For a better understanding of the invention and to show how it may be carried into effect, embodiments thereof will now be described, by way of example, with reference to the accompanying drawings, in which:

FIG. 1 illustrates in elevation and in axial section a first apparatus according to the invention,

FIG. 2 is a section along 22 of the apparatus illustrated in FIG. 1,

FIG. 3 is the electric circuit diagram of the apparatus illustrated in FIG. 1,

FIGS. 4 and 5 are curves illustrating the operation of the apparatus according to FIG. 1,

FIG. 6 is the electric circuit diagram of the apparatus illustrated in FIG. 1, comprising a modification according to the invention, and

FIG. 7 is a curve diagram illustrating the operation of the apparatus comprising the electric circuit illustrated in FIG. 6.

FIG. 1 illustrates a conductor wire 10 of which one portion is subjected to an electrolytic treatment by means of an apparatusaccording to the invention, this wire portion constituting one of the electrodes of the apparatus under consideration, which also comprises a tank 20, an electrolyte 30, another electrode 40, called the counterelectrode in the present description, and an electric circuit 50.

The wire 10 extends through the wall of the tank at 21 and 22 and that portion of this wire which "is situated between 21 and 22, i.e., the treated wire portion 100, is immersed in the electrolyte, as also is the counterelectrode.

Planes PI and P2 perpendicular to the treated wire portion 100 and containing the ends 21 and 22 of this wire portion also contain the ends 41 and 42 of the counterelectrode.

In the following, there will be considered the behavior of the elements of the apparatus in various sections of the latter through planes parallel to the other planes P1 and P2 and comprised between these planes or identical therewith. A section of the apparatus through a plane Px will be generally denoted by Sx.

The shape and arrangement of the elements are such that, during the passage of an electrolyzing current, the distribution of this current in any section of the apparatus is uniform in the electrolyte inthe neighborhood of the wire.

In the apparatus according to the invention as illustrated in FIG. 1, the wire portion subjected to the electrolytic treatment is rectilinear and the counterelectrode is formed of a helically coiled conductor wire having the same axis as the said treated wire portion. Considering any section Sx (FIGS. 1 and 2) of the apparatus through a plane Px perpendicular to the treated wire portion 100, the distribution of the electrolyzing current in the electrolyte in the neighborhood of the wire is uniform as shown in FIG. 2, in which the vectors indicate the quantity and the direction of the electrolyzing current at various points of the electrolyte in the neighborhood of the wire.

The electric circuit 50 (FIGS. 1 and 3) comprises an electrolyzing current source 51 and a compensating current source 52 including means 520 for adjusting the value thereof. The electrolyzing current source 51 is connected at 510 to a portion 102 of the wire which is situated outside the tank, and to one of the ends 41 of the counterelectrode 40. The compensating current source 52 is connected to the ends 41 and 42 of the counterelectrode 40.

During the passage of an electrolyzing current, a continuous distribution of this current is set up in the electrolyte along the treated wire portion and along the counterelectrode. The components of this electrolyzing current determine a voltage drop between the ends 21 and 22 of this wire portion 100 and between the ends 41 and 42 of the counterelectrode 40. Under these conditions, and in the absence of a compensating current in the counterelectrode, the curves representing the value of the potential along the treated wire portion and along the counterelectrode have the form indicated in FIG. 4.

In this figure, the curves A and B represent the value of the potential V of the various points of the treated wire portion 100, on the one hand, and of the counterelectrode 40 on the other hand, as a function of the distance x of these points from that section S1 of the apparatus which contains that end 21 of the treated wire portion which is not connected to the electrolyzing current source 51.

Assuming that the electrolyzing current density is absolutely constant along the treated wire portion and along the counterelectrode, the curves A and B are portions of a parabola whose axes are parallel to the axis of the ordinates and whose apices are respectively the points representing the potential of the wire in the section S1 and the potential of the counterelectrode in the section S2.

In any section Sx of abscissa x, the potential of a point a of the treated wire and that of a point b of the counterelectrode are Vax and Vbx respectively. In such a section, the potential difference between the anode and the cathode is then:

The value of this potential difference in a section of the apparatus determines the electrolyzing current density and consequently the quality of the electrolytic treatment which is obtained in this section of the apparatus. The application of a potential difference higher than the predetermined critical value disturbs the properties of the product obtained by the electrolytic treatment carried out under the above-indicated conditions. It is therefore necessary to keep this potential difference below the said critical value in any section of the apparatus. Now, this potential difference varies as a function of the abscissa x of the section of the apparatus, because the potential varies differently along the anode and along the cathode. More particularly, this potential difference generally assumes, as shown in FIG. 4, different values AVI and AV2 in the extreme sections 81 and S2 ofthe apparatus.

By passing a compensating current through the counterelectrode in accordance with the invention, there is produced in the latter a voltage drop which, for a predetermined value of the said current, equalizes the potential differences obtained between the anode and the cathode in the sections S1 and S2, or more generally in any two given sections of the apparatus, during the passage of an electrolyzing current of given value.

Such a compensating current is obtained, in the embodiment of the invention which is illustrated in FIG. 1, by employing the compensating current source 52 and actuating adjusting means 520 in such manner that this source supplies the said current of predetermined value. In the following, it will be assumed that the compensation is correct when this condition has been satisfied.

FIG. 5 shows the form taken by the curves A and B when the compensation is correct, i.e., when the compensating current fed into the counterelectrode equalizes the potential differences AW and AV2 obtained between the anode and the cathode in the sections S1 and S2 of the apparatus during the passage of an electrolyzing current ofgiven value.

As illustrated in FIG. 5, the potential difference AVx between the anode and the cathode which is obtained in any section Sx of the apparatus comprised between the sections S1 and S2 is lower than that obtained in these sections S1 and S2. Consequently, if the electrolyzing current and the compensating current are so chosen as to produce in the two extreme sections S1 and 52 a potential difference between anode and cathode which is equal to or lower than the aforesaid critical value, the electrolytic treatment will produce the desired effects in all the sections of the apparatus.

In order also to obtain a given degree of uniformity of the effects of the electrolytic treatment along the treated wire portion, it is necessary to ensure that the amplitude of the variations of the potential difference between anode and cathode along this treated wire portion remains below a given value.

It is to be noted that the amplitude of this variation is deduced from the extent and the direction of the deflection of each of the curves A and B. In the ease of FIG. 5, the direction of the deflection fa of the curve A is opposite to that of the deflection flz of the curve B. On examination of the phenomena involved in the apparatus according to the invention, it is found that the extent of the deflection of the curve A is approximately proportional to the resistance of the treated wire portion, and that the extent of the deflection of the curve B is approximately proportional to the resistance of the counterelectrode. If the resistance of the treated wire portion is sufficiently low, and the deflection of the curve A is consequently small, it may be sufficient to employ a counterelectrode whose resistance is so low that the amplitude of the variation of the potential difference between anode and cathode along the treated wire portion remains below the aforesaid given value.

In accordance with the invention, it is possible to modify the apparatus illustrated in FIG. 1 in such manner as to reduce the amplitude of this variation regardless of the value of the resistance of the wire subjected to the electrolytic treatment. This modification consists in supplying the electrolyzing current to the counterelectrode, not at one of the ends of the latter as in the apparatus illustrated in FIG. I, but at a point intermediate between its two ends as in FIG. 6, which shows the electrolyzing current source 51 connected to the counterelectrode 40 at a point M situated in the section Sm of the apparatus through a plane Pm perpendicular to the treated wire portion between the extreme sections S1 and S2.

FIG. 7 illustrates the form then taken by the curves A and B when the correct compensation is effected. It will be seen that the curve B has a cusp C of abscissa m corresponding to the point of connection M of the counterelectrode and that, if the chords which subtend the curves A and B are traced in FIG. 7, the deflections fa and lb of these curves are of like direction and of similar dimensions.

In the apparatus whose operating diagram is given in FIG. 7, the resistance of the treated wire portion and that of the counterelectrode are such that the particular value of the potential difference between anode and cathode which is obtained in the extreme sections S1 and S2 is also obtained in two other sections Sg and Sh of abscissae g and h respectively, that is to say, that:

Iclaim:

1. In apparatus for electrolytically treating an elongated conductive member, wherein said apparatus includes a tank for containing an electrolyte, means for supporting said member in said electrolyte containing tank, an electrode disposed in said electrolyte containing tank opposite to said member and extending through said electrolyte containing tank in the same direction as said member, an electrolyzing current source, and means coupling a first terminal of said electrolyzing current source to said member near the end of said tank and a second terminal of said electrolyzing current source to said electrode, whereby electrolyzing current flows between said electrode and said member through electrolyte contained in said tank the improvement comprising:

a compensating electric current source, and means electrically coupling said compensating current source to said electrode to provide a flow of compensating current therethrough in a direction and with an amplitude to minimize variations in the value of potential difference between points of said member and corresponding opposed points of said electrode.

2. The improved apparatus of claim 1, wherein said second terminal of said electrolyzing current source is coupled to a point substantially midway between the ends of said electrode.

3. The improved apparatus of claim 1, wherein said second terminal of said electrolyzing current source is coupled to said electrode near the end of said tank opposite to the coupling point of said first terminal.

4. The improved apparatus of claim 3, wherein a first ter minal of said compensating current source is coupled to said electrode near said one tank end and a second terminal of said compensating current source is coupled to said electrode near said opposite tank end.

5. The improved apparatus of claim 4, wherein said compensating current has a direction and an amplitude during the flow of said electrolyzing current to provide a potential difference between two spaced-apart points along said electrode equal to the potential difference between corresponding opposed points of said member, and wherein each of said spaced-apart points is near a respective end of said electrode.

6. The improved apparatus of claim 4, wherein said compensating current has a direction and an amplitude during the flow of said electrolyzing current to provide a potential difference between a point of said electrode near said one tank end and the corresponding opposed point of said member equal to the potential difference between a point of said electrode near said opposite tank end and the corresponding opposed point of said member.

7. in a process for electrolytically treating an elongated conductive member by immersing said member in a tank containing an electrolyte and comprising an electrode disposed opposite to said member and extending through said electrolyte in the same direction as said member, and wherein an electrolyzing current is caused to flow between said electrode and said member, the improvement comprising: providing the flow of a compensating current through said electrode to minimize variations in the value of potential difference between points of said member and corresponding opposed points of said electrode.

8. The process of claim 7, wherein said compensating current has a direction and an amplitude to provide a potential difference between a point of said electrode near one end thereof and the corresponding opposed point of said member equal to the potential difference between a point of said electrode near the other end thereof and the corresponding opposed point of said member. 

2. The improved apparatus of claim 1, wherein said second terminal of said electrolyzing current source is coupled to a point substantially midway between the ends of said electrode.
 3. The improved apparatus of claim 1, wherein said second terminal of said electrolyzing current source is coupled to said electrode near the end of said tank opposite to the coupling point of said first terminal.
 4. The improved apparatus of claim 3, wherein a first terminal of said compensating current source is coupled to said electrode near said one tank end and a second terminal of said compensating current source is coupled to said electrode near said opposite tank end.
 5. The improved apparatus of claim 4, wherein said compensating current has a direction and an amplitude during the flow of said electrolyzing current to provide a potential difference between two spaced-apart points along said electrode equal to the potential difference between corresponding opposed points of said member, and wherein each of sAid spaced-apart points is near a respective end of said electrode.
 6. The improved apparatus of claim 4, wherein said compensating current has a direction and an amplitude during the flow of said electrolyzing current to provide a potential difference between a point of said electrode near said one tank end and the corresponding opposed point of said member equal to the potential difference between a point of said electrode near said opposite tank end and the corresponding opposed point of said member.
 7. In a process for electrolytically treating an elongated conductive member by immersing said member in a tank containing an electrolyte and comprising an electrode disposed opposite to said member and extending through said electrolyte in the same direction as said member, and wherein an electrolyzing current is caused to flow between said electrode and said member, the improvement comprising: providing the flow of a compensating current through said electrode to minimize variations in the value of potential difference between points of said member and corresponding opposed points of said electrode.
 8. The process of claim 7, wherein said compensating current has a direction and an amplitude to provide a potential difference between a point of said electrode near one end thereof and the corresponding opposed point of said member equal to the potential difference between a point of said electrode near the other end thereof and the corresponding opposed point of said member. 